Drilling oil or gas wells with a drilling rig is a hazardous activity. One of the components of the drilling rig which creates a safety hazard to the workmen (roughnecks) is the exposed rapidly rotating drill stem. Regulators in certain jurisdictions have passed regulations which require employers to safeguard their workmen from accidentally coming into contact with moving parts of machinery or equipment that may be hazardous.
When an oil well is being drilled, it is customary, if the top layer of the formation to be drilled is gravel or if exceptional pressures are to be encountered, to set a conductor pipe in the hole extending the depth of the gravel to hold the gravel away from the drill stem or deal with the excess pressure. In other cases, however, where top formation gravel or exceptional pressures are not encountered, and to save time and money, the drill hole is started directly in the ground (spudded) and continues downwardly through the successive strata formations without a conductor pipe being set, until a suitable depth is reached to set the surface casing. The surface casing must be set in a competent formation and successfully cemented full length so that blow out preventers can be installed.
When an oil or gas well is being drilled, drilling mud is used to control formation pressures, cool the drill bit and remove formation cuttings (shale) generated by the rotating drill bit as it cuts downwardly through the strata formations. As the well is being drilled, the drilling mud is pumped downwardly through the interior of the rotating drill stem, which is hollow, and exits from the bottom of the rotating drill bit, which is of a diameter larger than the drill pipe. The drilling mud with shale cuttings returns to the surface in the annular space between the formation and the rotating drill stem. Since the returned drilling mud contains cuttings, the shale contaminated mud is pumped by a trash pump to a shale shaker where the shale is separated from the drilling mud. The mud from the shale shaker, with cuttings removed, is pumped by a mud pump to the top of the drill stem where it is again pumped down the interior of the rotating drill stem to the drill bit. The drilling mud is thus in continuous circulation while the well is being drilled.
When a drill hole is spudded without a conductor pipe being set, an annular space is created between the rotating drill stem and the surrounding ground. This annular space is usually filled with drilling mud which is being returned from the bottom of the hole. The drilling mud obscures the fact that there is an annular hole between the rotating drill stem and the surrounding ground.
While the well is being drilled, the rapidly rotating drill stem of the drilling rig and the annular hole in the ground around the rotating drill stem, as obscured by drilling mud, creates a potential safety hazard. Conditions under the platform floor are often wet and slippery from drilling mud and other debris that is spilled on the ground. Not infrequently, it is necessary for a rig worker to go below the drill deck and shovel or hose away debris and other unwanted materials from the area around the rotating drill stem. In such conditions, it is easy for the rig worker to lose his footing and fall, in some cases against the rotating drill stem and support apparatus. In other cases, the rig worker may inadvertently step into the obscured annular hole and contact the rotating drill stem or get his clothing caught in the rotating drill stem. Serious injury to the worker can then result. Sometimes, electrical equipment with electrical cord has to be taken below deck. The cord can become entangled in the rotating drill stem. Another problem that can occur in the drilling of oil wells is that unwanted articles can fall down the well bore. In such cases, drilling has to undergo a costly shut down while the unwanted articles are fished from the well bore.
U.S. Pat. No. 3,322,198, W. L. McHendry, issued May 30, 1967, discloses a safety device for enclosing a blowout preventer that has been fitted with a rotating head (pack-off). It is a second shield for venting any dust particles or gas that may get by the pack-off unit in the event of expiry of the rubber pack-off element. A blowout preventer is used while drilling the main section of an oil or gas well and can only be installed after the surface hole section (a larger diameter hole) is drilled and the surface casing is set and cemented full length. The surface casing is then cut and a casing head (flange) is welded on. The blowout preventer is then installed on the casing head. The McHendry device is useful only when air or mist drilling is being done on the main drill hole section. Air or mist drilling reduces drilling costs by increasing penetration rates but can only be done in areas that are known not to have a risk of formation water entering the wellbore. When drilling with air or mist and water is encountered, the well must be then filled with drilling mud which is circulated back to the shale shaker in a conventional procedure. In such cases, the air or mist drilling method cannot be continued. The device disclosed by McHendry comprises a split closable hood adapted to be mounted on the drilling head. The hood has a pair of open end portions. One of the end portions includes a mechanism for clamping the hood in a substantially sealed relation about a portion of the drilling head. The other of the end portions includes a collar and a flexible baffle inwardly directed from the interior surface of the collar. The baffle has a hole therein for accepting the drill string of the well drilling apparatus and for permitting entry of air into the hood. Means for withdrawing air and particles from the interior of the hood for controlled disposal is also included. The safety device is designed to fit around the blowout preventer at a fixed elevation and does not have legs which enable the height of the safety device to be adjusted.
Canadian Patent Application No. 2,395,963, N. D. Denis, filed Sep. 6, 2002, discloses a mesh-like percussive or rotary rock drill guard that is designed to keep a driller or operator away from the rotating drill rod of a seismic drilling rig. The guard is mounted on a rock drill mast and is connected to the rotation lever of the drill. Doors mounted on the mast will automatically encase the complete drill and drill rod upon activating any rotation lever. The guard does not have extendible legs which enable the elevation of the guard to be adjusted or plumbed. Seismic drilling rigs are small and portable compared to oil well drilling rigs which employ heavy and massive equipment.
The foregoing examples of the general art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.